Safety locking tool holder for pneumatic hammer

ABSTRACT

A safety locking holder for mounting an attachment tool onto a pneumatic hammer prevents tool removal when the holder is fully screwed onto the hammer. The holder includes a slotted collar and an open chamber portion which permit ready insertion and removal of an attachment tool when the holder is in nonlocking engagement with the hammer.

United States Patent 1 1 3,560,008

[ 72] inventor James 0. Taylor [56] 1 References Cited Lantana, Fla. UNITED STATES PATENTS Q 5 1 232 1,731,836 10/1929 Williams 279/19x 4 451 Patented Feb.2, 1971 21432114 12/1947 Elkms 279/194 [73] Assignee Florida Pneumatic Manufacturing FORElGN TENTS Corporation 713,196 8/1954 England 279/19 Lantana, Fla.

Primary ExaminerAndrew R. .luhasz Assistant ExaminerDonald D. Evenson Attorney-Larson and Taylor [54] L HOLDER FOR ABSTRACT: A safety locking holder for mounting an attachment tool onto a pneumatic hammer prevents tool 8 Claims snrawmg removal when the holder is fully screwed onto the hammer. [52] US. Cl

/19 The holder includes a slotted collar and an open chamber por- [51] Int. Cl B23b 31/06 tion which permit ready insertion and removal of an at- [50] Field of Search 279/19, tachment too] when the holder is in nonlocking engagement 19.6, 19]; l73/(lnquired);279/l9.4, 195 with the hammer PATENTEI] FEB 21971 3500.000

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FIG. 5'

NVENTO TTORNEY 5 0 JAMES o. TAYLOR SAFETY LOCKING TOOL HOLDER FOR PNEUMATIC HAMMER FIELD OF THE INVENTION The present invention generally relates to pneumatic hammers and more particularly to safety locking means for attachment tools adapted to be mounted onto pneumatic hammers.

THE PRIOR ART Pneumatic hammers impart a rapid reciprocatory movement to an attachment tool through the impact of a pneumatically operated reciprocating piston located within the hammer against the shank end of the tool. Many different types of attachment tools may be utilized and thus it is necessary to provide the hammer with means for mounting these tools which permits easy removal thereof so that one tool may be readily substituted for another.

In accordance with one such prior art tool holder a rigid coil spring adapted to be threadably received on the end of the hammer includes an outwardly extending portion thereof for supporting the tool. The support portion of the holder is formed substantially in the shape of an inverted U such that the tool body rests in the yoke of the U and a conventional flange formed between the shank and the tool body abuts against the U-shaped portion during operation. The holder support thus forms both a support for the tool as well as a limit stop for restricting the axial movement of the tool after impact with the hammer piston. The support portion of the holder is spaced from the body portion formed by the coils and this arrangement together with the U-shaped portion permits ready substitution of one tool for another without necessitating the unscrewing of the holder from the end of the hammer.

Although the holder described above provides easy tool replacement and generally effective support the holder suffers one major disadvantage, namely, too that the tool may be separated from the holder under working conditions. The support provided by the holder permits some lateral movement of the tool away from the yoke of the support portion and thus under certain circumstances such as where the hammer is held at an extreme angle against the work the tool may slip out of the holder and, under the force supplied by the hammer, cause damage or serious injury.

Attempts have been made to provide a holder which locks the tool into position to thus prevent the tool from flying off the hammer during operation thereof. In one such arrangement a holder is constructed from three separate elements including a solid body member having a threaded bore therethrough adapted to be received on the end of .a hammer. The holder further includes a two-piece generally cylindrical tool support formed by a pair of substantially identical members which when fitted together form an externally threaded end portion adapted to be received in the bore of the body member. The assembled tool support members also form a central bore for supporting the body portion of a chosen tool as well as a chamber communicating with the bore which determines the limits of motion of the tool. To replace one tool with another the two-piece support must be unscrewed from the body member, the tool removed from between the support members, the new tool placed between the members and the members fitted together therearound, and the reassembled support screwed back into the bore of the body member. It will be appreciated that this process is tedious particularly where it is necessary to replace tools with any frequency. Further, the fact that a three-piece construction is necessary increases the cost of manufacture and handling as well as the possibility of losing or misplacing any of the holder components. Thus it will be appreciated that although the arrangement described does provide generally effective locking of the tool within the holder it does so at the expense of a significant increase in the time required for mounting the tool on the hammer, in the number of component parts required and in the overall manufacturing an and handling cost of the holder.

SUMMARY OF THE INVENTION In accordance with the present invention there is provided a mounting device of the type described which enables easy mounting and removal of a pneumatic hammer attachment tool while providing effective locking of the attachment tool to prevent the tool from separating from the hammer and thus causing possible personal injury and/or physical damage. In accordance with the invention a mounting device or holder is provided wherein tightening" of the engagement of the mounting device beyond a predetermined point prevents removal of the attachment tool from the holder and thus provides a safety lock for the tool. Prior to this tightening the tool may be readily inserted into and removed from the holder.

In accordance with a presently preferred embodiment the mounting device of the invention is of unitary construction and includes a body portion adapted to be mounted on a pneumatic hammer and a slotted end portion for supporting the body of an attachment tool. The end portion and body portion are interconnected by intermediate portion which is formed to define an open chamber permitting reciprocating axial movement of the tool. This chamber communicates with a threaded bore in the body portion which set serves in mounting the tool holder onto the pneumatic hammer.

In operation of the attachment tool is disposed within the holder such that the body portion of the tool rests in the slot in the end portion of the holder, and the flange and the of the tool lie within the chamber and communicating bore. The shank extends into a bore in the hammer so that the end thereof may be contacted by the operating piston of the hammer during hammer operation. The holder is dimensioned relative to the length of the shank of the attachment such that the holder body may be securely threaded onto the hammer, i.e., with the end of the hammer extending substantial distance into the bore thereof, without impairing the ready insertion and removal features of the holder. Thus the holder need not be removed from the hammer when tool replacement or substitution is desired. However, in accordance with an important feature of the invention, when the holder body is threaded onto the hammer beyond a point corresponding to a predetermined depth of extent of the end portion of the hammer into the bore of the body of the tool is fixedly captured within the holder and the bore of the end portion of the hammer and cannot be removed. The difference between the locking and nonlocking positions of the holder body may conveniently be made one turn. Thus locking and unlocking of the tool onto the hammer is effected through a simple rotative manipulation of the body portion of the holder.

In accordance with a further feature of the present invention a biasing spring disposed within the holder chamber bears against the flange of the attachment tool and the face of the end portion of the hammer. This arrangement prevents contact of the end of the shank of the tool with the operating piston of the hammer except where the tool is pressed against the work and the biasing force of the spring is overcome.

BRIEF DESCRIPTION OF THE DRAWING Other features and advantages of the invention will become apparent upon consideration of the following description taken together with the accompanying drawings wherein:

FIG. I is a side elevation view of a pneumatic hammer incorporating a holder in accordance with a presently preferred embodiment of the invention;

FIGS. 2 and 3 are end and side elevation views, respectively, of a prior art holder;

FIG. 4 is an enlarged sectional side elevation view corresponding to FIG. 1 showing the cooperation between the tool, holder and hammer; and

FIG. 5 is a perspective view of the holder of FIGS. 1 and 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows the safety holder in accordance with a presently preferred embodiment of the invention mounted on an exemplary hammer generally denoted H. The hammer H includes a cylindrical body section having a handle member 12 depending downwardly therefrom and a barrel member 14 projecting outwardly therefrom. Extending outwardly of the handle 12 is a manually operable air pressure control device 16. A flexible line 18 depending from handle 12 connects the hammer H to a suitable source of compressed air. The hammer H includes an operating mechanism (not shown) for automatically reciprocating a piston 19 (FIG. 4). in a conventional manner. It will be understood that the particular details of the operating mechanism form no part of the present invention and pneumatic hammers other than that illustrated may be utilized. Reference may be made, for example, to US. Pat. No. 2,655,90l for the details of construction of a suitable operating mechanism.

The novel tool-mounting device or holder of the present invention generally denoted 20 is threadably engaged with barrel 14 of hammer H. Holder 20 mounts a suitable attachment tool 22 onto barrel 14 in a manner described hereinbelow. While a great number of different tools corresponding to tool 22 may be mounted on hammer 20 (tool 22 may for example be a chisel) these tools characteristically comprise, as may best be seen in FIG. 4, a shank 24, an intermediate annular flange 26 and a body portion 28 which includes the working portion (not shown) of the tool.

In order to provide a background for understanding the present invention a prior art attachment tool holder will be considered. Referring to FIGS. 2 and 3, there is shown a holder 30 comprising a rigid spring member which includes a tightly coiled body portion 32 adapted to mount the holder 30 onto a hammer and a spaced generally U-shaped support or collar portion 34. The coils 36 of body portion 32 are adapted to be threadable received in grooves formed in the barrel of a pneumatic hammer (not shown). The body portion 28 of a tool 22' shown in phantom in FIG. 2 and 3 rests in the yoke of U-shaped support portion 34 while a flange portion 26' abuts against the inner surface thereof as shown, the inner surface of support portion 34 serving as a limit stop for axial travel of the tool 22'. The shank 24 of the tool 22' extends into a longitudinal bore (not shown) in the hammer.

Tool 22 may be removed from holder 30 by lifting the body portion 24 out of U-shaped support 34 while simultaneously withdrawing the shank 24 from the bore in the barrel of the hammer. As discussed hereinabove although the holder arrangement of FIGS. 2 and 3 provides for ready insertion and removal of an attachment tool with this arrangement the tool is not prevented from separating from the holder under all circumstances. The forces described above which are exerted by a user in attempting to remove the tool from the holder may be reproduced during operation of the hammer under certain circumstances, thus causing separation of the tool and holder. An example of one such circumstance is where the tool is used such that the body portion thereof forms a small angle with the surface of the work so that significant pivoting of the tool takes place. If at this time the tool slides off the end of the work it may separate from the holder and fly off of the hammer.

Referring again to FIG. 1 and particularly to FIGS. 4 and 5 a holder 20 in accordance with the invention is shown. The holder 20 generally comprises a cylindrical body portion 40, and an intermediate half cylinder 42 which includes a longitudinal chamber 44, and a collar portion 46.

Body portion 40 includes a central bore 50 (FIG. 4) therethrough which is threaded as indicated at 52 to permit threadable engagement of the holder 20 with an externally threaded end portion 54 of barrel 14 (FIG. 4). Body portion 40 includes an outer lip 40a which limits the extent of travel of body 40 on end portion 54. Bore 50 communicates with a bore 54a formed in end portion 54 adapted to receive shank 24 of tool 22. Movement of shank 24 to the right as shown in FIG. 4 is limited by the abutment of an enlarged bell-shaped portion 7A0 thereof adjacent flange 26 with the portion of end portion 54 which defines the opening ofibore 54a. As is shown in FIG.

4 bore 54a includes a corresponding bell-shaped portion 54b at the opening thereof which mates with bell-shaped portion 24a to provide a snug fitting of tool 22 into bore 54a. Shank 24 in the extreme rightward position thereof extends well into piston chamber 19a thus enabling piston 19 to make solid impact therewith.

Collar 46 is of generally flat disclike construction and includes a generally U-shaped slot or recess 56 bounded on opposite sides by pronglike members 58 and 60 and adapted to receive and serve as a rest for the body portion 28 of tool 22.

Chamber 44 formed. in intermediate portion 42 of the holder 20 is generally semicircular in cross section and communicates with bore 50 and slot 56. The diameter of chamber 44 is such as to permit unimpeded axial travel of tool 22 therealong. Chamber-forming portion 42 includes a tapered stop portion 42a adjacent collar 46 which serves as abutment to limit the travel of tool 22. Thus with too] 22 mounted as shown in FIG. 4, tool 22 may move, under the impact provided by operating piston 19, between the point at which the bore-defining portion of end portion 54 of barrel l4 abuts with the enlarged portion 24a of shank 24 and the point at which the distal face of flange 26 abuts with stop portion 42a immediately adjacent collar 46.

A spring 62 (FIG. 4) prevents contact between shank 24 and piston 19 when the tool is not in use. Spring 62 is disposed between flange 26 of tool 22 and the face of end portion 54 of hammer H and includes a first loop 64 which surrounds and bears against portion 24a and a second loop 66 which bears against the end face of end portion 54. Spring 62 prevents, in the absence of other forces, movement of tool 22 (to the right as shown in FIG. 4) sufficient to permit contacting of shank 24 by piston 19. Spring 62 thus prevents injury or damage which might occur by inadvertent energization of the hammer. It will be understood that the biasing force furnished by spring 62 is relatively weak and is easily overcome by the pressing of the tool against the work. It will be further appreciated that under working conditions the tool is returned by rebounding against the work to a position where it receives the next blow from the piston and thus even in the absence of spring 62 inadvertent operation of the hammer I-[ will result in a single leftward movement of the tool 22.

As will be described in detail hereinbelow the axial position of holder 20 along end portion 5411 will determine whether or not the mounted tool 22 may be removed. Preferably, with the holder 20 fully screwed onto the hammer H the holder 20 is in a locking position whereas with the holder 20 less than fully screwed on, e.g., with the holder unscrewed by one turn or more from the fully screwed-on position, the holder is in a nonlocking position.

In operation, with the holder 20 in the nonlocking position thereof the tool 22 may be freely inserted into the holder by inserting the end of shank 24 into bore 544 and lowering body portion 28 into slot 56." It will be appreciated that as tool 22 is lowered into slot 56 the extent to which the shank 24 may be entered into bore 54a is increased and that with tool 22 parallel to the longitudinal axis of holder 20 the tool 22 is freely movable axially in the holder. In a similar manner tool 22 may be readily removed from the holder 20 by sliding the'tool axially away from the hammer barrel [4 and then lifting the tool body 28 out of slot 56. The positions of tool 22 and holder 20 before removal of the tool 22 are indicated in phantom in FIG. 4. Lifting of the tool 22 out of the lot 56 causes flange 26 to clear stop portion 42a which permits further slight axial movement of the tool 24 away from barrel 14 and thus permit final removal of the tool 22. The clearance between shank 24 and the bore 540 is such as to permit some pivoting of the upper surface of the end of shank 24 about the edge of end portion 54 forming the opening of bore 54a. This pivoting action enables the lower edge of shank 24 to clear bore 54a.

With holder 20 in the locking position thereof the entire holder including collar portion 46 is moved closer to barrel l4 and thus even with movement of tool 22 to the furtherest leftward position thereof as viewed in FIG. 4 the distance that shank 24 extends into bore 540 is such as to prevent sufficient pivoting of tool 22 to enable removal of the tool. In this position the pivot point about which the upper surface of shank 24 pivots is further from the end of shank 24 and the lower edge portion of the shank 24 cannot clear the bore 540. it is noted that the distance which dictates whether or not the tool 22 may be removed from the holder is that between the point where the distal face of the flange 26 contacts the stop portion 420 adjacent collar 46 and the point where the bell-shaped portion 54b of bore 540 begins. This latter point is critical, rather than the opening of bore 54a, because bell-shaped portion 54b permits relatively free pivoting of the end of shank 24. The clearance between the shank diameter and the bore diameter is also critical but is a predetermined and generally standard quantity.

To provide a specific example it is noted that for a standard tool having a shank corresponding to shank 24 measuring approximately l% inches from the distal surface of flange 26 to the end surface of the shank the critical distance described hereinabove, that is, the distance between the abutment point of flange 26 and stop 42a and the beginning of bell-shaped portion 54b, is approximately 1% inches. Thus, generally, where the distance between the abutment point of the flange 26 and stop 42a and the beginning of bell-shaped portion 54b is greater than this value the tool may be removed from the holder whereas where this distance is less than this value the tool cannot be removed. in actual practice the difference between the locking and unlocking positions of the holder may be made to correspond to the travel of the holder upon one complete turn of the holder body 40 on end portion 54, this difference corresponding to the distance between a position where the tool is securely locked and one where the tool is relatively easily removed.

It will be appreciated from the foregoing that the holder of the invention provides simple yet effective means for locking an attachment tool onto a pneumatic hammer without sacrificing of the ready insertion or removal features of the nonlocking prior art-holder devices. Further, the rugged unitary construction of the holder of the invention is obviously advantageous as compared with the multipiece locking holder described hereinbefore.

It will be further understood by those skilled in the art that the embodiment of the invention shown and described herein is subject to modification without departing from the scope and spirit of the invention. Accordingly, it should be understood that the invention is not limited by the exemplary embodiment shown and described but rather only be the subjoined claims.

I claim:

1. A tool-mounting device for mounting a flanged attachment tool having a body and a shank, onto a pneumatic hammer of the type including piston means for imparting a reciprocating movement to the attaching tool, said device comprising a unitary member including a body portion adapted to be mounted onto the pneumatic hammer through threadably engaging an end member of the hammer. an end portion for supporting the attachment tool, and means defining an open chamber connecting said end portion and said body portion for permitting axial movement of the tool, said device further comprising spring means located in said chamber for biasing an attachment tool received in said device out of contact with the piston means so that said reciprocating movement is not imparted to the tool until the tool is brought into contact with a workpiece, and said device being dimensioned such that tightening of the engagement of said body portion with the end member of the hammer beyond a predetermined position along the extent of the end member prevents removal of the attachment tool from the mounting device and such that an attachment tool may be inserted into said device and removed therefrom without necessitating removal of said device from the pneumatic hammer.

2. A tool-mounting device in accordance with claim 1 wherein said spring means comprises a coil spring includinga first end for engaging the end of the pneumatic hammer in which the attachment tool is inserted and a second end for engaging a flange portion of the attachment tool.

3. A tool-mounting device in accordance with claim 2 wherein said body portion includes a threaded bore therein for engaging an externally threaded end member of the hammer.

4. A tool-mounting device in accordance with claim 2 wherein said end portion includes a pair of outwardly extending spaced pronglike members forming a slot therebetween for receiving the body of an attachment tool.

5. A tool-mounting device in accordance with claim 4 wherein said slot includes a pair of spaced parallel straight line portions joined together at one end by a generally semicircular end portion.

6. A tool-mounting device in accordance with claim 4 wherein said body portion includes a central bore therethrough in communication with said open chamber, said bore being threaded to receive an externally threaded pneumatic hammer end member having a shank-receiving bore therein and being of such a length as to permit receipt of the end member of the hammer to such a depth as to prevent pivoting of an inserted attachment tool to the extent necessary to pemtit removal thereof from said slot formed in said end portion.

7. A tool-mounting device in accordance with claim 6 wherein one unlocking turn of said body portion is sufficient to permit removal of the attachment tool.

8. A tool-mounting device in accordance with claim 2 wherein said body portion comprises a generally cylindrically shaped member having a bore therein, said end portion comprises a disclike collar member including a pair of pronglike portions forming a slot therebetween, and said chamber-defining means comprises a half cylinder. 

1. A tool-mounting device for mounting a flanged attachment tool having a body and a shank, onto a pneumatic hammer of the type including piston means for imparting a reciprocating movement to the attaching tool, said device comprising a unitary member including a body portion adapted to be mounted onto the pneumatic hammer through threadably engaging an end member of the hammer, an end portion for supporting the attachment tool, and means defining an open chamber connecting said end portion and said body portion for permitting axial movement of the tool, said device further comprising spring means located in said chamber for biasing an attachment tool received in said device out of contact with the piston means so that said reciprocating movement is not imparted to the tool until the tool is brought into contact with a workpiece, and said device being dimensioned such that tightening of the engagement of said body portion with the end member of the hammer beyond a predetermined position along the extent of the end member prevents removal of the attachment tool from the mounting device and such that an attachment tool may be inserted into said device and removed therefrom without necessitating removal of said device from the pneumatic hammer.
 2. A tool-mounting device in accordance with claim 1 wherein said spring means comprises a coil spring including a first end for engaging the end of the pneumatic hammer in which the attachment tool is inserted and a second end for engaging a flange portion of the attachment tool.
 3. A tool-mounting device in accordance with claim 2 wherein said body portion includes a threaded bore therein for engaging an externally threaded end member of the hammer.
 4. A tool-mounting device in accordance with claim 2 wherein said end portion includes a pair of outwardly extending spaced pronglike members forming a slot therebetween for receiving the body of an attachment tool.
 5. A tool-mounting device in accordance with claim 4 wherein said slot includes a pair of spaced parallel straight line portions joined together at one end by a generally semicircular end portion.
 6. A tool-mounting device in accordance with claim 4 wherein said body portion includes a central bore therethrough in communication with said open chamber, said bore being threaded to receive an externally threaded pneumatic hammer end member having a shank-receiving bore therein and being of such a length as to permit receipt of the end member of the hammer to such a depth as to prevent pivoting of an inserted attachment tool to the extent necessary to permit removal thereof from said slot formed in said end portion.
 7. A tool-mounting device in accordance with claim 6 wherein one unlocking turn of said body portion is sufficient to permit removal of the attachment tool.
 8. A tool-mounting device in accordance with claim 2 wherein said body portion comprises a generally cylindrically shaped member having a bore therein, said end portion comprises a disclike collar member including a pair of pronglike portions forming a slot therebetween, and said chamber-defining means comprises a half cylinder. 